In Situ Spawning of Hydrothermal Vent Tubeworms (Riftia pachyptila).

Riftia pachyptila, the giant vestimentiferan tubeworm, dominates the biomass of many hydrothermal vent sites in the Gulf of California (Guaymas Basin) and on the East Pacific Rise and Galapagos Spreading Center (1). The worms typically occur in large clumps or thickets as mixed populations of males andfemales. On a dive series made by the submersible Alvin in the vicinity of 9{deg}50'N on the East Pacific Rise, I observed spawning tubeworms while I was sampling associated fauna. This note presents a brief account of the spawning activity.